1. Field of the Invention
The present invention relates to the field of electron emission and more specifically to methods and apparatuses using electron sources.
2. Description of the Related Art
Apparatuses and methods for incorporating conventional thermionic electron emission sources into devices, such as cathode ray tubes (CRTs), X-radiation tubes, or microwave tubes, are well known. Electron emission sources with better performance than common thermionic sources, such as field emission electron sources, may be less compatible with the apparatuses and methods designed for the common thermionic sources and can have their performance impaired by these apparatus and methods.
A common process for producing a vacuum tube 10, shown in FIG. 1, such as a CRT, involves securing an electron source or sources 12 to a support cap 14 that is a part of the electron gun structure 16 located in an end of the tube 10. A common support cap 14, illustrated in FIG. 2, is generally a cup or can shaped structure with at least one aperture 20 to allow electrons generated by the electron source to pass. Referring again to FIG. 1, a vacuum is commonly achieved in the tube by pumping the gas out of the tube through an opening 18 at the terminal end of the neck and then sealing the opening. When the gas is pumped out of the tube, the gas as well as particles of phosphor, DAG coating, or other particles existing in the tube may flow over the electron source. These particles may interfere with the emission properties of field emission electron sources and can even result in catastrophic electrical shorts.
Accordingly, apparatus and methods for preventing gas or particles present in the conventional processes of common electron source applications are needed to enable the benefits of improved electron sources to be more fully realized.